This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. We have recently found that Staphylococcus aureus bacteria calcify rapidly when incubated in serum. The objective of the present study is to determine the ultrastructural location of the mineral deposited into these bacteria. Our working hypothesis is that the mineral will be deposited within the cell wall since this structure has size exclusion characteristics similar to those of other matrices that are calcified in serum.